This invention relates generally to an open channel-type aerator for use in a liquid-containing basin, tank, or reservoir. More particularly, the invention relates to a low profile cascade postaerator disposed in a liquid-containing basin for the purpose of raising the dissolved oxygen (DO) concentration level of the basin effluent.
Until recently, most publicly and privately owned wastewater treatment facilities were not required to meet DO limits as criteria for discharge. Now, more stringent water quality standards Have been imposed by Federal Regulations governing the effluent limits of treatment facilities. Current criteria specify a DO concentration between 3 and 6 mg/l, depending on the receiving stream requirements. Most existing wastewater treatment facilities cannot meet the newly implemented DO criteria. Consequently, postaeration must be added for compliance.
Several known postaeration methods have been employed for oxygen transfer. In general, the methods most commonly used are various types of mechanical or conventional cascade aeration. Each of these methods has the disadvantage of being an expensive addition to existing wastewater treatment facilities.
Mechanical aeration requires the addition of an aeration basin with adequate liquid retention capacity for oxygen infusion by electrically powered aeration equipment. This is the least desirable method of boosting the oxygen levels, but in the past was the only available solution. There are two cost factors involved with mechanical aeration. First, the high initial investment for the basin and equipment; second, the ongoing maintenance and operating expense.
Cascade postaeration installations are more desirable and cost effective. There is no power consumption or maintenance expense, the primary requirement for the application of a cascade aerator being sufficient elevation to produce a water fall. The normal requirement for oxygen transfer through prior art cascade aeration is twelve inches of water fall for each mg/l increase. For example, to raise the oxygen concentrations 6 mg/l, a minimum fall of six feet typically would be required. Most existing facilities lack ample elevation for the utilization of prior art cascade aerators.
It will thus be appreciated that postaeration as the final stage of treatment is rarely without considerable expense, initially or in operation and maintenance.